1. Field of the Invention
The invention relates to threaded tubular connection components used, for example, in oil applications, and more precisely relates to protecting the female end of certain of such components.
The term “component” as used here means any element or accessory used to drill or operate a well and intended to be connected by means of a threading to another component to constitute a threaded tubular connection with that other component. The component may, for example, be a relatively great length tube (in particular about ten meters in length), a tubular coupling a few tens of centimeters long, an accessory for such tubes (a hanger, a cross-over, a safety valve, a tool joint, a sub or the like).
2. Description of Related Art
The components are generally connected to each other for dropping into a hydrocarbon or the like wells and constitute a drill string, a casing string, or liner string or a tubing string (working strings)
Specification API 5CT from the American Petroleum Institute (API), equivalent to International Standard ISO 11960: 2004 from the International Standardisation Organisation (ISO) governs tubes used as casing or tubing, and specification API 5B defines standard threadings for such tubes.
API specification 7 defines threaded joints with a shoulder for rotary drill rods.
The manufacturers of threaded tubular connection components have also developed premium threaded connections which have threadings with specific geometries, and specific means providing them with better performance in service, in particular as regards mechanical strength and seal. Examples of such premium threaded connections and those specific means are described in patents EP 488 912, U.S. Pat. No. 4,494,777 and EP 0 767 335.
The components cited above include a threaded female end which is intended to be made up into a threaded male end of another drilling or working component. Thus, it is vital that their female end be damaged, polluted or deteriorated as little as possible from the moment they leave their production line to the moment of use, and also between two successive uses. It will be understood that it is necessary to protect not only the internal threading but also the annular surface or surfaces (sealing or abutment) which each have specific and complementary functions, in particular as regards providing a seal during use, against corrosion, dust and shocks (or blows).
The ends of said components are generally coated just before coupling with a grease with anti-galling properties. API RP 5A3 (formerly API Bul 5A2) or ISO 13678: 2000 defines such greases and the modes of application of such greases are described in API RP 5C1. However, the greases in document API RP 5A3 suffer from a number of disadvantages linked to their toxic constituent content, in particular lead, to the excess quantity of grease applied and to the need to apply the grease just prior to dropping the components into the well.
Thus, in particular in patent documents U.S. Pat. No. 6,933,264, U.S. Pat. No. 6,869,111 and WO 2003/102457, it has been proposed to replace the grease applied with a brush at the completion of production to the end of the component by a factory-applied thin layer of a predetermined thickness of a “semi-dry” lubricant which is free of heavy metals. Particularly in patent documents U.S. Pat. No. 6,027,145, EP 1 211 451 and FR-05/10503 (unpublished patent application), it has been proposed to replace the grease applied with a brush at the end of production to the end of the component by a factory-applied thin layer of a predetermined thickness of a dry lubricant based on particles of solid lubricants.
In those cases in which a dry or semi-dry lubricant is factory-applied, it is also and even more necessary to protect the layer of lubricating product with which the ends of the component are coated as much as possible as well from mechanical removal as from pollution (sand, debris) which are prejudicial to the effectiveness of the lubricating product.
To obtain such protection, in general, as required by specification API 5CT (paragraph 12.2), a protective device is placed on the male and female ends of the threaded tubular connection components. Many devices of that type have been proposed for the female ends, in particular in patent documents EP 0 148 807 and US-2006/0042709.
This latter document more particularly aims at protectors for connections which have been previously coated with a lubricant applied in the factory. The protector described comprises a body provided with, on the one hand, an external threading intended to cooperate with the internal threading of the female end to be protected, and on the other hand, first and second annular type flexible sealing elements placed respectively downstream and upstream of the external threading and intended to provide first and second seals at the respective internal and end annular surfaces which are placed upstream and downstream of the internal threading of the female end. The first sealing element is intended to envelope the zone containing the internal annular surface of the female end while providing a bearing seal. As it is relatively bulky, it is poorly adapted for accommodating dimensional differences between the female end and/or its protector resulting from manufacture and/or temperature variations. Further, it can deform in the event of large temperature variations and thus no longer be in intimate contact with the internal annular surface of the female end, thus encouraging spontaneous unscrewing of the protector in the presence of vibrations, primarily generated during transport and/or temperature variations that may vary from −40° C. to +80° C.